In the Applicant's co-pending application Ser. No. 12/435,740, the entire contents of which are explicitly incorporated herein by reference, there is described a system and method for determining whether an interaction with a webpage at a client browser is a human dependent interaction. In this system, event streams generated at a user interface are analyzed and compared with previously recorded event streams from known human interactions and known non-human interactions. The comparison indicates whether the current interaction is likely to be a human dependent interaction. In the Applicant's co-pending application Ser. No. 12/435,751, the entire contents of which are explicitly incorporated herein by reference, the process of analyzing an event stream is enhanced by invoking effects on the user interface and then analyzing the resultant event stream to see how a user responded to an invoked effect. Responses to the invoked effects may be characteristically human or characteristically non-human.
What is required is a system, method and computer readable medium that can invoke additional behavior at the user interface without substantially affecting existing applications running in web pages nor affect legitimate web crawlers or computer assisted humans.